Genetic regulation of feed intake and energy balance in poultry

Function of Amino Acids and Neuropeptides in Feeding Behavior in Chicks

Regulation of food intake, especially during the neonatal period, is important to ensure optimal nutrition and meet the metabolic requirements of growing and healthy animals. However, many problems associated with neonatal chicks remain unsolved. Feeding behavior during the neonatal stage is characterized by short resting periods between very brief times spent taking up food. Accordingly, neuropeptides, which take time to synthesize and release, as well as nutrients that are taken up via feeding, may be involved in feeding regulation. The present review summarizes current knowledge about the role of amino acids and their interaction with neuropeptides on the regulation of food intake in neonatal chicks with special emphasis on L-arginine metabolism and neuropeptide Y. Fasting and subsequent short-term refeeding influence amino acid metabolism in the brain. Short-term refeeding induces a rapid increase in the concentrations of several amino acids, which may contribute to satiety signals in the neonatal chick brain. The function of L-arginine is related to its metabolite, L-ornithine, which acts as an innate satiety signal in the control of food intake. Co-injection with L-ornithine attenuates the orexigenic effect of neuropeptide Y in a dose-dependent manner. This implies a potent interaction in the brain between the regulation of food intake by neuropeptide Y and acute satiety signals by L-ornithine. The roles of other amino acids in feeding and their relationship with the stress response are also discussed in this review. In conclusion, endogenous neuropeptides and endogenous and/or exogenous nutrients such as amino acids are believed to coordinate the feeding behavior of neonatal chicks.

Dietary supplementation of lysozyme can improve growth rate, laying performance, blood biochemistry, and mRNA levels of some related genes in different plumage-colored quails

The impact of dietary lysozyme (LZ) supplementation on the growth and laying performance was investigated over 4 weeks of growing and 6 weeks of laying periods in two different plumage color (white and brown-feathered) Japanese quail varieties. For each variety, 240 birds were randomly assigned into four groups with four replicates for each group. The first group (control) was fed a basal non-supplemented diet (BD). Whereas the 2nd, 3rd, and 4th received the BD supplemented with commercial LZ (CLZ) at 100 mg/kg diet, and natural LZ (NLZ) at 100 and 200 mg/kg diet, respectively. The main findings included significant increases in body weights and gains in the white-feathered quails supplemented with NLZ1 compared to the control and NLZ2. However, there were no significant differences in the case of brown-feathered quails in all LZ supplementations. Moreover, the different dietary LZ lowered FI in both quails with the lowest intake observed in the brown-feathered quails. Accordingly, enhanced FCR was reported in the CLZ groups for both quail varieties and in NLZ1 and NLZ2 for the white-feathered and brown-feathered quails, respectively. In both quail varieties, the NLZ2 significantly lowered serum creatinine and urea and increased albumen and globulin levels compared with other groups. Histologically, the best hepatic histological features were found in both quail' varieties fed the NLZ1-supplemented diet. Accompanying LZ-induced modulations in the expression levels of GHR, IGF-1, leptin, CCK, FAS, and ACC genes in both quail varieties were reported. Besides, both quail varieties in NLZ1& NLZ2 supplementation exhibited significant increases in hen day egg production, egg weight, egg mass, and hatchability percentages along with differences in external and internal egg qualities compared with LZ-free diet or CLZ. Therefore, NLZ could be used as an effective feed supplement to enhance the growth and egg performance of Japanese quail with caution being drawn to the supplementation dose about quail variety.

Optimising Growth, Immunity, and Gene Expression in Broiler Chickens Through Dietary Threonine Levels and Oil Inclusion

BACKGROUND

The inclusion of synthetic amino acids in poultry nutrition plays a crucial role in both enhancing the synthesis of immunoglobulins and elevating the overall comprehensiveness of the amino acid profile.

OBJECTIVES

This research examined the effects of consuming threonine (Thr) in various forms levels with low or high oil on broiler chickens' growth and immunity.

METHODS

We investigate the growth performance, feed efficiency, immune response, intestinal morphology, absorptive capacity, and expression of some genes related to the feed intake (Pro-opiomelanocortin [POMC]), fatty acid synthesis (Acetyl-CoA Carboxylase [ACC]), immunity (lipopolysaccharide-induced tumour necrosis like alpha factor [LITAF]), and heat shock protein 70 (HSP70). Eight groups of chicks were used, including four dietary Thr levels (100%, 115%, 130%, or 145%) with two oil levels (mixture of sunflower 50% and soybean oils 50%): (control) and high.

RESULTS

The higher dietary Thr level (145%) with high oil inclusion significantly increased ACC and POMC gene expression, resulting in the lowest feed intake, body weight gain (BWG), and liver fat content. Combining high oil with 115% Thr was the optimum for the broilers. The birds have significant (p ≤ .05) growth performance, immune parameters, and intestinal health, as well as the lowest expression of ACC, POMC, HSP70, and LITAF, which was reflected in better feed conversion ratio and lower incidence of fatty liver, thermo-resistance, and immune status of the birds.

CONCLUSIONS

The combination of high oil and 115% Thr levels optimises broiler health and productivity, enhancing growth, immune function, and gut health. This diet lowers the expression of genes associated with fatty liver and stress, leading to better feed efficiency, thermo-resistance, and overall well-being. Adopting these dietary adjustments can improve broiler performance and economic viability in poultry farming by enhancing essential productivity metrics.

Distinct patterns of feed intake and their association with growth performance in broilers

Improving feed utilization is a vital strategy to meet the growing global demand for meat and promote sustainable food production. Over the past few decades, significant improvements in the feed intake (FI) and feed utilization efficiency of broilers have been achieved through advanced breeding procedures, although dynamic changes in FI and their effects on the feed conversion ratio (FCR) have remained unclear. In this study, we measured individual weekly FI and body weight of 274 male broilers to characterize the dynamic FI patterns and investigate their relationship with growth performance. The broilers were from 2 purebred lines and their crossbreed and measurements were collected from 4 to 6 wk of age. Overall, a continuous increase in the weekly FI occurred from 4 to 6 wk of age, whereas the body weight gain (BWG) reached an inflection point in wk 5. The dynamic change in weekly FI was observed to follow 3 distinct FI patterns: pattern 1, a continuous weekly increase in FI; pattern 2, an increase followed by a plateau; pattern 3, an increase followed by a decrease. The prevalence of these patterns was similar in the purebred and crossbred populations: pattern 2 was most frequent, followed by a moderate proportion of pattern 1, and the lowest proportion of pattern 3. Broilers following pattern 1 displayed significantly better growth performance and feed utilization efficiency than those following pattern 3, emphasizing the importance of maintaining good appetite in the last stage of broiler production. In summary, this study has characterized the dynamic patterns of FI and their association with growth performance. Our results offer a new foundation for improving feed utilization efficiency and investigating feeding regulation in broilers.

Daily feeding frequency affects feed intake and body weight management of growing layers

The objective of this study was to investigate the effect of feeding behavior on feed intake and body weight in growing layers and the underlying mechanisms, thereby providing a scientific foundation for optimal feeding practices in growing layers' management. A total of 144 Hy-line brown growing layers of 10 wk old and similar body weight, were divided into 3 treatment groups with different feeding frequency and equal cumulative daily feeding amount: the once-a-day feeding group (F1) was fed at 9:00 am every day, with feeding amount of 150 g/layer; the twice-a-day feeding group (F2) were fed at 9:00 am and 13:00 pm every day, with each feeding amount of 75 g/layer; the 4 times-a-day feeding group (F4) were fed at 9:00 am, 11:00 am, 13:00 pm, and 15:00 pm every day, with each feeding amount of 37.5 g/layer. Pre-experiment lasted for 1 wk and formal experiment lasted for 8 wk. The results indicated that the daily feed intake and body weight were decreased (P < 0.05) while feed conversion ratio was not affected (P > 0.05) as daily feeding times increased. The glandular stomach proportion was significantly increased in twice-a-day feeding group, while liver proportion and ileum length were significantly increased in 4 times-feeding group (P < 0.05). Additionally, 4 times-feeding daily resulted in a significant elevation of blood glucose levels, which may have suppressed feed intake (P < 0.05). In 4 times-feeding group, the plasma triglyceride levels increased as feeding times, accompanied by a notable up-regulation in the mRNA level of appetite-suppressing gene, hypothalamic pro-opiomelanocortin (POMC) and glandular stomach ghrelin. This modulation effectively suppressed the subsequent feed intake and body weight. Therefore, 4 times feeding daily is recommended in growing layers' management, because it reduced the feed cost without affecting the feed conversion efficiency.

The effect of spexin injection and its interaction with nitric oxide, serotonin, and corticotropin receptors on the central regulation of food intake in broilers

Complex homeostatic control mechanisms are tools to adjust the food birds eat and their appetite. Birds and mammals differ in several ways considering food intake regulation. Therefore, this study aimed to investigate the special effects of the intracerebroventricular (ICV) injection of spexin and its interaction with nitric oxide, serotonin and corticotropin receptors on central food intake regulation in broilers. In the test 1, Broilers received ICV injection of saline, PCPA (p-chlorophenylalanine,1.25 µg), spexin (10 nmol) and PCPA+spexin. In test 2-7, 8-OH-DPAT, SB-242084 (5-HT2C, 1.5 µg), L-arginine (Precursor of nitric oxide, 200 nmol), L-NAME (nitric oxide synthetize inhibitor, 100 nmol), Astressin-B (30 µg) and Astressin2-B (30 µg) were injected to Broilers instead of the PCPA. Then, the amount of food received was measured up to 2 h after the injection. The food consumption was significantly decreased by Spexin (10 nmol) (P<0.05). Concomitant injection of SB-242084+spexin attenuated spexin-induced hypophagia (P<0.05). Co-injection of L-arginine+spexin enhanced spexin-induced hypophagia and this effect was reversed by L-NAME (P<0.05). Also, concomitant injection of Astressin-B + spexin or Astressin2-B + spexin enhanced spexin-induced hypophagia (P<0.05). Founded on these observations, spexin-induced hypophagia may be mediated by nitric oxide and 5-HT2C, CRF1, and CRF2 receptors in neonatal broilers.

Low-Protein Diets Differentially Regulate Energy Balance during Thermoneutral and Heat Stress in Cobb Broiler Chicken (Gallus domesticus)

The objective was to assess whether low-protein (LP) diets regulate food intake (FI) and thermogenesis differently during thermoneutral (TN) and heat stress (HS) conditions. Two-hundred-day-old male broiler chicks were weight-matched and assigned to 36 pens with 5-6 chicks/pen. After 2 weeks of acclimation, birds were subjected into four groups (9 pens/group) including (1) a normal-protein diet under TN (ambient temperature), (2) an LP diet under TN, (3) a normal-protein diet under HS (35 °C for 7 h/day), and (4) an LP diet under HS, for 4 weeks. During HS, but not TN, LP tended to decrease FI, which might be associated with a lower mRNA abundance of duodenal ghrelin and higher GIP during HS. The LP group had a higher thermal radiation than NP under TN, but during HS, the LP group had a lower thermal radiation than NP. This was linked with higher a transcript of muscle β1AR and AMPKα1 during TN, but not HS. Further, LP increased the gene expression of COX IV during TN but reduced COX IV and the sirtuin 1 abundance during HS. The dietary protein content differentially impacted plasma metabolome during TN and HS with divergent changes in amino acids such as tyrosine and tryptophan. Compared to NP, LP had increased abundances of p_Tenericutes, c_Mollicutes, c_Mollicutes_RF9, and f_tachnospiraceae under HS. Overall, LP diets may mitigate the negative outcome of heat stress on the survivability of birds by reducing FI and heat production. The differential effect of an LP diet on energy balance during TN and HS is likely regulated by gut and skeletal muscle and alterations in plasma metabolites and cecal microbiota.

Central dopaminergic, serotoninergic, as well as GABAergic systems mediate NMU-induced hypophagia in newborn chicken

AIM

Dopaminergic, serotoninergic, and GABAergic systems influence feeding; however, it is unknown how these chemicals interact with neuromedin U (NMU)-induced feeding in birds. In the current study, ten trials were conducted to determine the links between the above-mentioned systems and NMU.

MATERIALS AND METHODS

In the foremost experimentation, chickens were given intracerebroventricularly injections of NMU (0.1, 1, and 10 µg). NMU (10 µg), SCH23390 (5 nmol), a D1 receptor antagonist, and NMU + SCH23390 were administered in the second experiment. In subsequent experiments, instead of SCH23390, were applied AMI-193 (5 nmol D2 receptor antagonist), NGB2904 (6.4 nmol D3 receptor antagonist), L-741,742 (6 nmol D4 receptor antagonist), 6-OHDA (2.5 nmol dopamine inhibitor), SB242084 (5-HT2c receptor antagonist, 1.5 μg), 8-OH-DPAT (5-HT1A receptor agonist, 15.25 nmol), picrotoxin (GABAA receptor antagonist, 0.5 μg), and CGP54626 (GABAB receptor antagonist, 20 ng). Then, cumulative intake of food was recorded for 2 h.

RESULTS

According to the results, NMU reduced feeding when compared to the control group (p < 0.05). The NMU-induced hypophagia was reduced with co-injection of NMU and SCH23390 (p < 0.05). Hypophagia was diminished with NMU and AMI-193 (p < 0.05). NMU + NGB2904 and NMU + L-741,742 co-injections had no influence (p > 0.05). 6-OHDA reduced the hypophagia (p < 0.05). NMU and SB242084 decreased the hypophagia (p < 0.05), whereas NMU and 8-OH-DPAT had no effect (p > 0.05). The effects were amplified with picrotoxin (p < 0.05). NMU with CGP54626 had no influence on the hypophagia (p > 0.05).

CONCLUSION

Thus, NMU-induced hypophagia is probably mediated by D1/D2, 5-HT2c, and GABAA receptors in neonatal chicks.

Applications of Enteroendocrine Cells (EECs) Hormone: Applicability on Feed Intake and Nutrient Absorption in Chickens

This review focuses on the role of hormones derived from enteroendocrine cells (EECs) on appetite and nutrient absorption in chickens. In response to nutrient intake, EECs release hormones that act on many organs and body systems, including the brain, gallbladder, and pancreas. Gut hormones released from EECs play a critical role in the regulation of feed intake and the absorption of nutrients such as glucose, protein, and fat following feed ingestion. We could hypothesize that EECs are essential for the regulation of appetite and nutrient absorption because the malfunction of EECs causes severe diarrhea and digestion problems. The importance of EEC hormones has been recognized, and many studies have been carried out to elucidate their mechanisms for many years in other species. However, there is a lack of research on the regulation of appetite and nutrient absorption by EEC hormones in chickens. This review suggests the potential significance of EEC hormones on growth and health in chickens under stress conditions induced by diseases and high temperature, etc., by providing in-depth knowledge of EEC hormones and mechanisms on how these hormones regulate appetite and nutrient absorption in other species.

Evaluation of dynamic effects of dietary medium-chain monoglycerides on performance, intestinal development and gut microbiota of broilers in large-scale production

Medium-chain monoglycerides (MG) have been reported to affect the productive performance, gut microbiota and health of broiler chickens reared in ideal experimental conditions at home and abroad. However, the effects of MG on performance, intestinal development and gut microbiota of chickens in large-scale farms during different feed stages remain unknown. The present study was conducted on a modern farm with a total of 12,000 yellow feathered broiler chicks that were randomly allotted to 2 groups (1000 chicks/replicate, 6 replicates/group) for a 70-day trial. The control group (CON group) received a basal diet, and the treated group (MG group) was fed a basal diet containing 300 mg/kg mixed MG. The results revealed that dietary MG significantly (P < 0.05) increased the body weight and average feed intake, but notably reduced the feed conversion and mortality of chickens in large-scale production during the starter phase. The villus height of the duodenum in the MG group at 1, 2 and 7 wk of age increased notably, and the villus height to crypt depth ratio at 1, 2, 5 and 10 wk of age was improved. Dietary MG decreased the serum insulin content of chickens at 5, 7 and 10 wk of age, and decreased the serum lipopolysaccharide at 3 and 7 wk of age. The triglyceride level of chickens at 3, 5 and 10 wk of age and the low-density lipoprotein cholesterol level of chickens at 7 and 10 wk of age in the MG group decreased notably, while the high-density lipoprotein cholesterol increased significantly. Moreover, MG supplementation selectively increased the relative abundance of genus Bacteroides (family Bacteroidaceae) and Lachnospiraceae_NK4A136_group, but decreased the content of genus Rikenellaceae_RC9_gut_group, Collinsella and family Barnesiellaceae in the cecum of chickens at 3, 7 and 10 wk of age. Conclusively, these findings showed that dietary MG notably enhanced chicken performance, health and feed nutrient utilization at early ages by regulating gut microbiota, intestinal development and serum biochemical indices.

Hypophagia induced by intracerebroventricular injection of apelin-13 is mediated via CRF1/CRF2 and MC3/MC4 receptors in neonatal broiler chicken

Previous studies have shown the role of apelin and its receptors in the regulation of food intake. In the present study, we investigate the mediating role of melanocortin, corticotropin, and neuropeptide Y systems in apelin-13- induced food intake in broilers. Eight trials were run in the current investigation to ascertain the relationships between the aforementioned systems and apelin-13 on food intake and behavioral changes after apelin-13 administration. In experiment 1, hens were given an intracerebroventricular administration of a solution for control in addition to apelin-13 (0.25, 0.5, and 1 µg). Astressin-B (a CRF1/CRF2 receptor antagonist, 30 µg), apelin-13 (1 µg), and administration of astressin-B and apelin-13 concurrently, were all injected into the birds in experiment 2. Experiments 3 through 8 were quite similar to experiment 2, with the exception of astressin2-B (CRF2 receptor antagonist, 30 µg), SHU9119 (MC3/MC4 receptor antagonist, 0.5 nmol), MCL0020 (MC4 receptor antagonist, 0.5 nmol), BIBP-3226 (NPY1 receptor antagonist, 1.25 nmol), BIIE 0246 (NPY2 receptor antagonist, 1.25 nmol), and CGP71683A (NPY5 receptor antagonist, 1.25 nmol) were injected instead of astressin-B. After then, total food consumption was monitored for 6 h. Apelin-13 injections of 0.5 and 1 µg decreased feeding (P < 0.05). The hypophagic effects of apelin were attenuated following the simultaneous administration of Astressin-B and Astressin2-B with apelin-13 (P > 0.05). Co-infusion of SHU9119 and apelin-13 reduced the appetite-decreasing effects of apelin-13 (P > 0.05). When MCL0020 and apelin-13 were injected at the same time, the hypophagia that apelin-13 induced was eliminated (P > 0.05). BIBP-3226, BIIE 0246, and CGP71683A had no effect on the hypophagia brought on by apelin-13 (P > 0.05). Also, apelin-13 significantly increased number of steps, jumps, exploratory food, pecks and standing time while decreased siting time (P < 0.05). These findings suggest that apelin-13-induced hypophagia in hens may involve the CRF1/CRF2 and MC3/MC4 receptors.

Development of active jejunal glucose absorption in broiler chickens

Growth in chickens, especially meat-type chickens (broilers), is extremely rapid, but studies on the regulatory mechanism of intestinal glucose absorption with growth are few, contradictory, and unclear. Here, we investigated the regulation of intestinal glucose absorption with growth in broiler chickens using oral glucose gavage, intestinal Evans blue transit, intestinal glucose absorption, scanning electron microscopy, and glucose absorption- and cell junction-related gene expression analyses. Peak blood glucose levels after oral glucose gavage occurred at 10 and 50 min in chickens at 1 wk (C1W) and 5 wk (C5W) of age, respectively. The area under the curve for glucose levels was greater for the C5W than the C1W (P = 0.035). The stain ratio in the small intestine in the C5W was lower than that in the C1W (P = 0.01), but there were no differences in the tissue regions stained with Evans blue and the migration distance of Evans blue from Meckel's diverticulum. In everted sac and Ussing chamber experiments, we observed reduced intestinal glucose uptake and electrogenic glucose absorption in the jejunum of the C5W. Phloridzin, an inhibitor of sodium/glucose cotransporter 1 (SGLT1), suppressed the glucose-induced short-circuit current in the C1W (P = 0.016) but not the C5W. Although the addition of NaCl solution stimulated the glucose-induced short-circuit current in the C1W, no differences between the treatments were observed (P = 0.056), which was also the case in the C5W. Additionally, tissue conductance was diminished in the C5W compared with that in the C1W. Moreover, in the C5W, the intestinal tract was more developed and the jejunal villi were enlarged. In conclusion, glucose absorption throughout the intestine could be greater in C5W than in C1W; however, reduced SGLT1 sensitivity, decreased ion permeability, and intestinal overdevelopment lead to decreased local glucose absorption in the jejunum with growth in broiler chickens. These data provide a detailed analysis of intestinal glucose absorption in growing broiler chickens, and can contribute to the development of novel feeds.

Central Interaction Between L-Ornithine and Neuropeptide Y in the Regulation of Feeding Behavior of Neonatal Chicks

Ornithine has been identified as a potential satiety signal in the brains of neonatal chicks. We hypothesized that brain nutrient signals such as amino acids and appetite-related neuropeptides synergistically regulate food intake. To test this hypothesis, we investigated the interaction between neuropeptide Y (NPY) and ornithine in the control of feeding behavior in chicks and the associated central and peripheral amino acid metabolic processes. Five-day-old chicks were intracerebroventricularly injected with saline, NPY (375 pmol), or NPY plus ornithine (2 or 4 μmol) at 10 μl per chick, and then subjected to ad libitum feeding conditions; food intake was monitored for 30 min after injection. Brain and plasma samples were collected after the experiment to determine free amino acid concentrations. Co-injection of NPY and ornithine significantly attenuated the orexigenic effect induced by NPY in a dose-dependent manner. Central NPY significantly decreased amino adipic acid, asparagine, γ-aminobutyric acid, leucine, phenylalanine, tyrosine, and isoleucine levels, but significantly increased lysine levels in the brain. Co-injection of NPY and ornithine significantly increased ornithine and proline levels in all examined brain regions, but decreased diencephalic tryptophan and glycine levels compared with those of the control and NPY-alone groups. Co-injection of NPY and high-dose ornithine significantly decreased methionine levels in all brain regions. Central NPY significantly suppressed the plasma concentrations of amino acids, including proline, asparagine, methionine, phenylalanine, tyrosine, leucine, isoleucine, glycine, glutamine, alanine, arginine, and valine, and this reduction was greater when NPY was co-injected with ornithine. These results suggest that brain ornithine interacts with NPY to regulate food intake in neonatal chicks. Furthermore, central NPY may induce an anabolic effect that is modified by co-injection with ornithine.

Intake of nutrients (polyunsaturated fatty acids, tocols, and carotenes) and storage efficiency in different slow-growing chickens genotypes reared in extensive systems

An extensive rearing system (ERS) for poultry requires an outdoor run, which enhances the foraging activity of chickens. Slow-growing (SG) strains are more adapted to ERS than fast-growing (FG); and generally, have higher levels of bioactive compounds in their meat. The aim of this paper was to assess the storage efficiency of n-3 and n-6 polyunsaturated fatty acids (PUFA), tocols and carotenes in the meat of seven commercial SG genotypes (SG1-7). One hundred SG chicks/strain of both sexes were included and their walking activity (High- or Low-W) was classified: SG1-4, HW comprised more than 10% of the time budget, and SG5-7, less than 10% (LW). Chickens were reared in pens (4 pens/strain) with indoor (0.10 m2/bird) and outdoor (4 m2/bird) areas, and they were fed the same diet ad libitum (starter feed for 1-21 d, grower feed from 22 d to slaughter at 81 d). The chickens were weighed weekly; feed consumption and grass intake were also estimated. At 81 days of age, 32 chickens/genotype were selected on the basis of the average weight (1:1, M:F) and slaughtered. The breast, thigh and drumstick meat were excised from 30 carcasses/genotype, sampled and stored at -20°C until analysis. Nutrients (e.g., n-3, n-6, carotenes and tocols) of feed, grass and meat were analyzed. The storage efficiency of nutrients was estimated as the ratio between the amount deposited in the body muscles (OUT) and the dietary intake (feed and grass, IN). The genotype affected chickens foraging behavior and the intake of nutrients. For SG1, SG2 and SG3, more than 50% of the intake of n-3 came from grass, whereas in the other genotypes, less than 20%. Accordingly, chickens that foraged more showed better meat nutritional profiles (less fat, more n-3 and antioxidants), which, in ERS, was ascribed to grass ingestion. However, the storage efficiency of nutrients into meat was inversely correlated with the grass intake: strains with higher grass intake (SG1, SG2, and SG3) had lower storage rates. Several hypotheses were proposed to explain these trends.

Effects of residual feed intake divergence on growth performance, carcass traits, meat quality, and blood biochemical parameters in small-sized meat ducks

Feed efficiency (FE) is a major economic trait of meat duck. This study aimed to evaluate the effects of residual feed intake (RFI) divergence on growth performance, carcass traits, meat quality, and blood biochemical parameters in small-sized meat ducks. A total of 500 healthy 21-day-old male ducks were housed in individual cages until slaughter at 63 d of age. The growth performance was determined for all the ducks. The carcass yield, meat quality, and blood biochemical parameters were determined for the selected 30 high-RFI (HRFI) and 30 low-RFI (LRFI) ducks. In terms of growth performance, the RFI, feed conversion ratio (FCR), and average daily feed intake (ADFI) were found to be significantly lower in the LRFI group (P < 0.01), whereas no differences were observed in the BW and body weight gain (P > 0.05). For slaughter performance, no differences were observed in the carcass traits between the LRFI and HRFI groups (P > 0.05). For meat quality, the shear force of breast muscle was significantly lower in the LRFI group (P < 0.05), while the other meat quality traits of breast and thigh muscles demonstrated no differences (P > 0.05). For blood biochemical parameters, the serum concentrations of triglycerides (TG) and glucose (GLU) were significantly lower in the LRFI group (P < 0.05), while the other parameters showed no differences (P > 0.05). The correlation analysis demonstrated a high positive correlation between RFI, FCR, and ADFI (P < 0.01). The RFI demonstrated a negative effect on the breast muscle and lean meat yields, but a positive effect on the shear force of breast muscle (P < 0.05). Further, the RFI demonstrated a positive effect on the TG and GLU levels (P < 0.05). These results indicate that the selection for low RFI could improve the FE of small-sized meat ducks without affecting the production performance. This study provides valuable insight into the biological processes underlying the variations in FE in small-sized meat ducks.

Opioid receptor μ, not δ and κ modulate food intake induced by ghrelin in laying chickens

Evidence from animal studies suggests that opioidergic system and gherlin have a regulatory role in food intake, but their interaction(s) have not been studied in laying chickens. So in this study, 4 experiments (each included 4 groups) were designed. The first experiment was performed to evaluate the effect of ghrelin on the cumulative food intake. Experiments 2 to 4 were designed to investigate the possibility of μ, δ, or κ opioid receptors mediating ghrelin-induced hypophagia. All drugs were injected intracerebroventricularly (ICV) at 5 days of age. The results of this study showed that the ICV injection of 1.5 nmol ghrelin did not affect cumulative food intake. But ICV injection of ghrelin with doses of 3 and 6 nmol significantly reduced the cumulative food intake (p<0.05). However, co-injection of ghrelin with NTI, and nor-BNI did not show a significant change in decreased food intake compared to ghrelin. Also, opioid μ receptor gene expression significantly increased (p<0.05), but δ and κ opioid receptors gene expression did not significantly change. These results indicated the opioidergic system is involved in developing ghrelin-induced hypophagic effects in laying chickens. Accordingly, this effect of ghrelin to modify the nutritional behavior is possibly mediated by opioid μ receptor.

Mutations in melanocortin-4 receptor: From fish to men

Melanocortin-4 receptor (MC4R), expressed abundantly in the hypothalamus, is a critical regulator of energy homeostasis, including both food intake and energy expenditure. Shortly after the publication in 1997 of the Mc4r knockout phenotypes in mice, including increased food intake and severe obesity, the first mutations in MC4R were reported in humans in 1998. Studies in the subsequent two decades have established MC4R mutation as the most common monogenic form of obesity, especially in early-onset severe obesity. Studies in animals, from fish to mammals, have established the conserved physiological roles of MC4R in all vertebrates in regulating energy balance. Drug targeting MC4R has been recently approved for treating morbid genetic obesity. How the MC4R can be exploited for animal production is highly worthy of active investigation.

Characterization of differential gene expression of broiler chicken to thermal stress in discrete developmental stages

Prolonged exposure to high temperatures is linked to a range of physiological responses in broiler chickens including reduced disease resistance, low growth rate, and high mortality rate. In this study, we investigated the effect of heat stress on gene expression levels in 4-week-old and 6-week-old chickens each exposed to environments conditioned at thermoneutral (21 °C) and high (32 °C) temperatures. The analysis of differentially expressed genes (DEGs) using microarray revealed that genes underlying reactive oxygen species (ROS) production, cell nutrient intake, glucose metabolism, and circadian rhythm were differentially regulated in association with heat stress. We also found that the deviation in expression levels across the transcriptome in response to heat stress was significantly stronger (P< 2.2×10-16) in 6-week-olds compared to younger chickens. We finally observed a significant trend (r = 0.78, P< 2.2×10-16) that genes with a higher estimate of expression in the microarray were more likely to have a higher expression level in RNA-sequencing. Together, our findings provide comprehensive insights into the physiology involved in stress responses at varying developmental stages, which may facilitate chicken breeding to maximize their productivity under adverse conditions.

Dietary phosphorus level regulates appetite through modulation of gut and hypothalamic expression of anorexigenic genes in broiler chickens

Two experiments were designed to elucidate gut and hypothalamic molecular regulation of appetite by dietary phosphorus (P) concentration in broiler chickens. Birds (192 Cobb-500 broiler chickens) were randomly assigned to 3 experimental diets in experiment 1 (Exp. 1) and 24 broiler chickens were randomly assigned to 3 treatment groups in Exp. 2. Each diet comprised 8 replicate cages, with either 8 birds (Exp. 1) or 1 bird (Exp. 2) per replicate cage. In Exp. 1, diets contained 1.2 (P-deficient), 2.8 (P-marginal) or 4.4 (P-adequate) g/kg non-phytate P (nPP). In Exp. 2, birds fed the P-adequate diet were pair-fed (PF) to the feed consumption levels of birds fed the P-deficient diet. Feed intake and BW gain (P < 0.001) decreased in birds fed the P-deficient diet in Exp. 1. Birds fed the P-deficient diet had similar feed intake and BW gain with PF group fed the P-adequate diet (Exp. 2) but was significantly lower (P < 0.001) than birds fed the P-adequate diets. Sodium-phosphate cotransporter (NaPi-IIb) mRNA was upregulated (P < 0.05) in both experiments. Conversely, cholecystokinin (CCK) mRNA was downregulated (P < 0.01) in birds fed P-deficient diets. Anorexia-related hypothalamic cholecystokinin receptor (CCKAR) and melanocortin receptors (MC3R and MC4R) were upregulated (P < 0.05) in birds fed P-deficient diets, in both experiments. The current data show that dietary P deficiency decreases feed intake in broiler chickens by altering the expression of anorexigenic genes in the gut and hypothalamus of broiler chickens.

Research Note: Fine mapping of sequence variants associated with body weight of Lueyang black-boned chicken in the CCKAR gene

Cholecystokinin A receptor (CCKAR) is a key receptor mediating satiety. Previous studies found that decreased expression of CCKAR attenuated satiety, and thus contributed to the high-growth of broiler chickens. The objective of this study is to map sequence variants associated with the growth of chickens in the CCKAR. The CCKAR and upstream 1.4 kb genomic sequences were resequenced to find out all sequence variants using 35 Lueyang black-boned chickens (LBC). Haplotypes were reconstructed using the PHASE program. Linkage disequilibrium between variants was analyzed using the Haploview software. Associations of 33 tag SNPs that captured 89% of all variants with body weight of LBC (n = 675) at 16 (BW16), 20 (BW20) weeks of age and the onset (BWOEP) of egg production were tested using linear mixed models. A total of 126 SNPs were found and formed 41 haplotypes in 35 resequenced samples. Average length of haplotype blocks is 129 bp, indicating that LBC maintains low linkage disequilibrium at the CCKAR locus. Eleven of 33 tag SNPs were significantly associated with BW16, but not with BW20 and BWOEP. These significantly associated variants were most (8/11) distributed in a 2 kb region (chr4:73206169-73208244) around the Exon3. They together with 33 captured variants potentially disrupted binding sites of 471 transcription factors. Twelve variants can disrupt appetite (FOXO1) or lipid metabolism-related TF (AR and C/EBP) motifs. This study recognized chr4:73206169-73208244 as a key region harboring functional variants affecting the growth of chickens.

De-oiled soy lecithin positively influenced growth performance, nutrient digestibility, histological intestinal alteration, and antioxidant status in turkeys fed with low energy diets

1. The purpose of this research was to investigate the effects of supplementing an emulsifier (de-oiled soybean lecithin (DSL)) in a low metabolisable energy (ME) diet on growth performance, nutrient digestibility, carcase characteristics, intestinal morphology, blood metabolites, and antioxidant status in growing turkeys.2. A total of 480 one-day-old turkeys were assigned to one of four dietary treatments with of eight replicates of 15 birds each. Experimental treatments included a basal diet (BE) with commercially recommended levels of ME, a reduced energy diet (RE) with 0.42 MJ/kg reduction in dietary ME content, the RE diet + 1 g/kg DSL (DSL-1), and RE + 2 g/kg DSL (DSL-2).3. After 112 days, the body weight, average daily gain, and feed:gain in turkeys fed the supplemented for BE diets were better (P < 0.05) than in those fed RE, and those fed diet DSL-2 had the best performance. Although the RE diet decreased abdominal fat and relative liver weight (P < 0.05), compared to the BE diet, and supplementation with either level of DSL did not influence these variables.4. There were linear increases (P < 0.05) in fat digestibility, nitrogen-corrected apparent ME, and duodenal villus height, villus height/crypt depth ratio, and villus surface area in LE diet supplemented with DSL. From the jejunal morphology, crypt depth was decreased by DSL-supplemented diets (P < 0.05).5. Serum triglyceride, total cholesterol, and malondialdehyde concentrations were lower, whereas the serum superoxide dismutase activity was greater for the DSL-2 group compared to the BE and RE groups (P < 0.05).6. The findings suggested that, while low-ME diets impaired turkey growth performance, dietary supplementation of DSL could reverse such impacts of these diets. The DSL-supplemented diet at the inclusion level of 2 g/kg was advantageous over both BE and RE diets in terms of intestinal morphology, lipid profile, and antioxidant status in growing turkeys.

Effects of Dietary Energy Level on Performance, Plasma Parameters, and Central AMPK Levels in Stressed Broilers

This study aimed to characterize the effects of diets with different energy levels on the growth performance, plasma parameters, and central AMPK signaling pathway in broilers under dexamethasone (DEX)-induced stress. A total of 216 1-day-old male broiler chickens were allocated to groups fed with high (HED), National Research Council-recommended (control), or low (LED) energy diets. At 10 days old, chickens were treated with or without dexamethasone (DEX, 2 mg/kg body weight) for 3 consecutive days. HED increased broiler average daily gain (ADG) at 10 days old, compared with the LED (P < 0.05), while average daily feed intake (ADFI) and feed conversion rate (FCR) decreased as the dietary energy level increased (P < 0.05). Chickens fed a HED had higher total protein (TP) content, albumin (ALB), glucose (GLU), total cholesterol (TCHO), high-density lipoprotein (HDL) cholesterol, and low-density lipoprotein (LDL) cholesterol, compared with the control group (P < 0.05). At 13 days old, DEX decreased ADG and increased FCR in broilers fed with different energy diets (P < 0.05). The DEX-HED group had a higher ADFI than non-DEX treated HED group chickens. In addition, TP, ALB, triglycerides (TG), TCHO, HDL, and LDL content levels in the DEX group were higher than those in the control group (P < 0.05). The uric acid (UA) content of the LED group was higher than that of the HED group (P < 0.05). Further, gene expression levels of liver kinase B1, AMP-activated protein kinase α1, neuropeptide Y, and GC receptor in the hypothalamus were increased in chickens treated with DEX (P < 0.05). There was a trend toward interaction between plasma TCHO and hypothalamic LKB1 expression (0.05 < P < 0.1). In conclusion, this study suggests that HED improves growth performance, plasma glucose and total cholesterol at 10 days old broilers, but had no significant effect on performance, plasma parameters, and central AMPK in stressed broilers.

Comparison of Selection Signatures between Korean Native and Commercial Chickens Using 600K SNP Array Data

Korean native chickens (KNCs) comprise an indigenous chicken breed of South Korea that was restored through a government project in the 1990s. The KNC population has not been developed well and has mostly been used to maintain purebred populations in the government research institution. We investigated the genetic features of the KNC population in a selection signal study for the efficient improvement of this breed. We used 600K single nucleotide polymorphism data sampled from 191 KNCs (NG, 38; NL, 29; NR, 52; NW, 39; and NY, 33) and 54 commercial chickens (Hy-line Brown, 10; Lohmann Brown, 10; Arbor Acres, 10; Cobb, 12; and Ross, 12). Haplotype phasing was performed using EAGLE software as the initial step for the primary data analysis. Pre-processed data were analyzed to detect selection signals using the ‘rehh’ package in R software. A few common signatures of selection were identified in KNCs. Most quantitative trait locus regions identified as candidate regions were associated with traits related to reproductive organs, eggshell characteristics, immunity, and organ development. Block patterns with high linkage disequilibrium values were observed for LPP, IGF11, LMNB2, ERBB4, GABRB2, NTM, APOO, PLOA1, CNTN1, NTSR1, DEF3, CELF1, and MEF2D genes, among regions with confirmed selection signals. NL and NW lines contained a considerable number of selective sweep regions related to broilers and layers, respectively. We recommend focusing on improving the egg and meat traits of KNC NL and NW lines, respectively, while improving multiple traits for the other lines.

The AMPK-mTOR signaling pathway is involved in regulation of food intake in the hypothalamus of stressed chickens

Glucocorticoids (GCs) can stimulate the appetite and AMPK in broilers. The activation of hypothalamic mTOR has been proposed as an important anorexigenic signal. However, inhibitory effect of AMPK activity on appetite and AMPK downstream signaling pathway under stress has not been reported. In this study, we performed an intracerebroventricular (icv) injection of compound C, an AMPK inhibitor, in GC-treated birds to explore the regulatory mechanism on appetite and AMPK downstream signaling pathway. A total of 48 7-day-old broilers, which had received an icv cannula, were randomly subjected to one of two treatments: subcutaneous injection of dexamethasone (DEX) or saline. After 3 days of continuous DEX injection, chicks of each group received an icv injection with either compound C (6 μg/2 μL) or vehicle (dimethyl sulfoxide, 2 μL). The results showed that body weight gain was reduced by the DEX treatment. Compared with the control, icv injection of compound C reduced feed intake at 0.5-1.5 h. In the DEX-treated group, the inhibitory effect of compound C on appetite remained apparent at 0.5-1 h. The DEX treatment increased the gene expression of liver kinase B1 (LKB1), neuropeptide Y (NPY), and decreased p-mTOR protein level. In stressed broilers, inhibition of AMPK relieved the decreased mTOR activity. A significant interaction was noted in DEX and compound C on protein expression of phospho-AMPK. Taken together, in stressed broilers, the central injection of compound C could inhibit central AMPK activity and reduce appetite, in which the AMPK/mTOR signaling pathway might be involved.

Adenosine 5'-monophosphate induces hypothermia and alters gene expressions in the brain and liver of chicks

The adenosine A1 receptor is important for body temperature regulation in mammals; however, little is known about its function in avian species. In this study, we investigated the effects of the adenosine A1 receptor agonist and antagonist (adenosine 5'-monophosphate [5'-AMP] and 8 p-sulfophenyl theophylline [8-SPT], respectively) on thermoregulation in chickens. Male chicks were used in this study. After administration of 5'-AMP and 8-SPT, the rectal temperature, plasma metabolites, and gene expressions in the hypothalamus and liver were measured. The rectal temperature was reduced by peripheral administration of 5'-AMP, and the hypothermic effect of 5'-AMP was attenuated by central injection of 8-SPT in chicks. In the hypothalamus, the mRNA level of the agouti-related protein (AgRP) was increased by 5'-AMP administration, whereas it was suppressed by 8-SPT. The plasma levels of free fatty acid were elevated in 5'-AMP-treated chicks and that elevation was suppressed by the 8-SPT treatment. The gene expression of proopiomelanocortin in the hypothalamus was affected by 8-SPT. Nevertheless, the gene expressions of the thermoregulation-related genes, such as the thyrotropin-releasing hormone, were not affected by 5'-AMP and 8-SPT. Hepatic gene expressions related to lipid intake and metabolism were suppressed by 5'-AMP. However, the gene expression of the uncoupling protein was upregulated by 5'-AMP. Based on these results, birds, like mammals, will undergo adenosine A1 receptor-induced hypothermia. In conclusion, it is suggested that 5'-AMP-mediated hypothermia via the adenosine A1 receptor may affect the central melanocortin system and suppress hepatic lipid metabolism in chickens.

Effects of fasting and re-feeding on the expression of CCK, PYY, hypothalamic neuropeptides, and IGF-related genes in layer and broiler chicks

Cholecystokinin (CCK) and peptide YY (PYY) have been investigated as gut hormones that send satiation signals to the brain in mammals. There is evidence that chicken PYY mRNA expression was the highest in the pancreas compared to other tissues. We recently suggested that insulin-like growth factor (IGF)-1 and its binding proteins (IGFBPs) may be involved in the appetite regulation system in chicks. In the present study, in order to evaluate the possible roles of CCK, PYY, and IGF-related proteins in the appetite regulation system in chicks, we analyzed changes in the mRNA levels of these genes in response to fasting and re-feeding in layer and hyperphagic broiler chicks. In layer chicks, 12 h of fasting reduced the mRNA levels of intestinal CCK, PYY, Y2 receptor, and pancreatic PYY, and these changes were reversed by 12 h of re-feeding. On the other hand, in broiler chicks 12 h of fasting reduced the mRNA levels of intestinal PYY and Y2 receptor, but not intestinal CCK and pancreatic PYY, and these changes were reversed by 12 h of re-feeding. Hypothalamic NPY mRNA significantly increased by 12 h of fasting in both chicks, and these changes were reversed by re-feeding. Also, 12 h of fasting significantly increased the mRNA levels of hypothalamic agouti-related protein and reduced the mRNA levels of hepatic IGF-1 only in broiler chicks, and 12 h of re-feeding did not change these. IGFBP-1 and -2 mRNA levels were markedly increased by 12 h of fasting in both chicks, and these changes were reversed by re-feeding. IGFBP-3 mRNA levels were increased by 12 h of fasting only in layer chicks, while re-feeding reduced the mRNA levels of IGFBP-3 in both types of chicks. These results suggest that several peripheral hormones, such as pancreatic PYY and intestinal CCK, may not play important roles in the regulation of food intake in broiler chicks.

Chemerin impairs food intake and body weight in chicken: Focus on hypothalamic neuropeptides gene expression and AMPK signaling pathway

Unlike mammals, the role of adipokines and more particularly of chemerin in the regulation of food intake is totally unknown in avian species. Here we investigated the effect of chemerin on the food and water consumption and on the body weight in chicken. We studied the effects on the plasma glucose and insulin concentrations and the hypothalamic neuropeptides and AMPK signaling pathway. Female broiler chickens were intraperitoneally injected, daily for 13 days with either vehicle (saline; n = 25) or chemerin (8 μg/kg; n = 25 and 16 μg/kg; n = 25). Food and water intakes were recorded 24 h after each administration. Overnight fasted animals were sacrificed at day 13 (D13), 24 h after the last injection and hypothalamus and left cerebral hemispheres were collected. Chemerin and its receptors protein levels were determined by western-blot. Gene expression of neuropeptide Y (Npy), agouti-related peptide (Agrp), corticotrophin releasing hormone (Crh), pro-opiomelanocortin (Pomc), cocaine and amphetamine-regulated transcript (Cart) and Taste 1 Receptor Member 1 (Tas1r1) were evaluated by RT-qPCR. In chicken, we found that the protein amount of chemerin, CCRL2 and GPR1 was similar in left cerebral hemisphere and hypothalamus whereas CMKLR1 was higher in hypothalamus. Chemerin administration (8 and 16 μg/kg) decreased both food intake and body weight compared to vehicle without affecting water intake and the size or volume of different brain subdivisions as determined by magnetic resonance imaging. It also increased plasma insulin levels whereas glucose levels were decreased. These data were associated with an increase in Npy and Agrp expressions and a decrease in Crh, Tas1r1 mRNA expression within the hypothalamus. Furthermore, chemerin decreased hypothalamic CMKLR1 protein expression and AMPK activation. Taken together, these results support that chemerin could be a peripheral appetite-regulating signal through modulation of hypothalamic peptides expression in chicken.

Av-UCP single nucleotide polymorphism affects heat production during cold exposure in chicks

OBJECTIVE

Uncoupling protein one (UCP1) is involved in thermogenesis, especially in non-shivering heat production. In chickens, a single nucleotide polymorphism (SNP) of the av-UCP (avian UCP) gene has been reported to be associated with body weight gain and increased abdominal fat. The purpose of this study was to examine the relationship between the av-UCP gene SNP and heat production in chicks.

METHODS

C/C and T/T male chicks (Rhode Island Red) of av-UCP gene SNP (g. 1270, C > T) were exposed to a low temperature environment (16 °C for 15 min) and their physiological responses were compared.

RESULTS

After cold exposure, mean rectal temperatures of C/C chicks were higher than those of T/T chicks. In pectoral muscle, genes expression of av-UCP and carnitine palmitoyltransferase-1 were higher in C/C chicks than T/T chicks. Hypothalamic expression levels of thyrotropin-releasing hormone and proopiomelanocortin genes were higher in C/C chicks than T/T chicks. Expression of hypothalamic corticotropin-releasing hormone, arginine vasotocin, brain-derived neurotrophic factor and neuropeptide Y genes did not differ between C/C and T/T chicks. In addition, plasma free fatty acid levels in C/C chicks were lower than those of T/T chicks.

CONCLUSION

These results suggest that the av-UCP gene SNP affects non-shivering heat production via the hypothalamo-pituitary-thyroid axis and fatty acid metabolism in the chicken.

Expression and localization of adiponectin and its receptors (AdipoR1 and AdipoR2) in the hypothalamic-pituitary-ovarian axis of laying hens

Adiponectin is a hormone secreted by adipose tissue that is involved in the regulation of energy homeostasis and reproduction. In this study, the expression levels of adiponectin and its receptors in the hypothalamic-pituitary-ovarian (HPO) axis of laying hens were investigated using quantitative real-time PCR (qRT-PCR) and Western blotting, and the localization of these proteins was explored using immunohistochemistry. The morphological relationships between adiponectin receptors and gonadotropin-releasing hormone (GnRH) neurons were analyzed using double immunofluorescence labeling. The results showed that adiponectin mRNA and protein were widely expressed in all tissues involved in the HPO axis in laying hens, with especially high expression in the hypothalamus. Both AdipoR1 and AdipoR2 were more highly expressed in the pituitary than in other tissues and exhibited similar mRNA and protein expression patterns. The immunohistochemistry results showed that adiponectin and AdipoR2 were localized in the major hypothalamic nuclei that regulate food intake and energy balance (i.e., the lateral hypothalamic area (LHA), infundibular nucleus (IN), dorsomedial nucleus (DMN), and paraventricular nucleus (PVN)). Immunostaining revealed that adiponectin and its receptors were also localized in the cytoplasm of cells in the adenohypophysis. In the ovaries, adiponectin was localized in the granulosa layer, in the theca externa of follicles and in basal cells, while AdipoR1 and AdipoR2 were localized in basal cells. In the double immunofluorescence labeling experiment, AdipoR1 and AdipoR2 were localized in GnRH neurons in the IN and DMN. These results suggest that adiponectin and its receptors may play major roles in the endocrine network, which integrates energy balance and reproduction.

Central and peripheral methylamine-induced hypophagia is mediated via nitric oxide and TAAR1 in neonatal layer-type chicken

The aim of the current study was to determine effects of intracerebroventricular (ICV) and intraperitoneal (i.p.) administration of Methylamine (MET) and possible interactions with nitric oxide (NO) and TAAR₁ pathways in 24-h fasted (FD₂₄) and ad libitum layer-type chicken. In experiment 1, FD₂₄ chicken ICV injected with MET (15, 30, 45, 60 and 75 μg). In experiment 2, ICV injection of MET (15, 30, 45, 60 and 75 μg) was injected in the ad libitum birds. Experiments 3-4 were similar to experiments 1-2, except chicken i.p. injected with MET (15, 30, 45, 60 and 75 mg/kg). In experiment 5, FD₂₄ birds ICV injected with l-NAME (NO synthesis inhibitor, 100 nmol), MET (75 μg) and co-injection of l-NAME + MET. Experiment 6 was similar to experiment 5, except, ad libitum birds received injections. In experiment 7, FD₂₄ chicken i.p. injected with l-NAME (100 mg/kg), MET (75 mg/kg) and co-injection of l-NAME + MET. In experiment 8, FD₂₄ birds ICV injected with RO5256390 (selective TAAR₁ agonist, 10, 20 and 40 μg). In experiment 9, ad libitum birds ICV injected with RO5256390 (10, 20 and 40 μg). In experiment 10, FD₂₄ birds ICV injected with RO5256390 (10 μg), MET (75 μg) and their co-injection. Experiment 11 was similar to experiment 10, except, ad libitum birds received ICV injections. In experiment 12, FD₂₄ chicken i.p. injected with RO5256390 (2.5, 5 and 10 mg/kg). In experiment 13, FD₂₄ chicken i.p. injected with RO5256390 (2.5 mg/kg), MET (75 mg/kg) and RO5256390 + MET. Then cumulative food intake was determined until 120 min after injection. According to the results, ICV injection of MET decreased food intake in FD₂₄ and ad libitum chicken (P < 0.05). MET (i.p.) diminished food consumption in fasted (P < 0.05) but not in ad libitum chicken (P> 0.05). Co-injection of the l-NAME + MET significantly decreased MET-induced hypophagia in FD₂₄ and ad libitum chicken (P < 0.05). MET-induced hypophagia (i.p.) weakened by l-NAME in FD₂₄ chicken (P < 0.05). RO5256390 decreased food intake in FD₂₄ and ad libitum chicken (P < 0.05). Co-injection of RO5256390 + MET increased MET-induced hypophagia in FD₂₄ and ad libitum chicken (P < 0.05). RO5256390 decreased food intake in FD₂₄ chicken (P < 0.05). Co-injection of the RO5256390 + MET amplified MET-induced hypophagia in FD₂₄ chicken (P < 0.05). Based on the findings, MET-induced hypophagia is mediated via NO and TAAR₁ pathways on food intake in layer chicken.

Improvement in broiler performance by feeding a nutrient-dense diet after a mild feed restriction

Background: The use of early nutrient-restriction programs in broilers can prevent complications such as increased body fat deposition and its consequences. However, feed restriction not always gives the expected results. Objective: To assess the effect of two levels of feed restriction followed by a re-alimentation period with five increasing nutrient levels on growth performance and immune response of broiler chickens. Methods: A total of 330 animals were used. The treatments were: 25 (T25) and 35% (T35) quantitative feed restriction during the starting period, and 0, 2.5, 5, 7.5, 10, and 15% increased energy and protein contents during the growing and finishing periods. Results: For all the T25 treatments, except for T25-0, feed intake (FI) and body weight gain (BWG) were higher, and feed conversion rate (FCR) was lower (p<0.05) compared to the control treatment. In that group, the response of FI and BWG to the increased nutrient density was mostly quadratic (p<0.001), whereas that of FCR was linear (p<0.001). The FI and BWG results were less homogeneous in the T35 treatments, but FCR was lower compared to the control treatment (p<0.05) in all of them. The FCR showed no differences (p>0.05) between treatments during the finishing period. Conclusion: Feeding a nutrient-dense diet after a period of mild feed restriction gives the best results, while increasing nutrient density after a more severe feed restriction does not improve productive results compared to a standard diet. Carcass traits and immune function were not affected by restriction level or nutrient density.

Identification of hub genes involved in apparent metabolizable energy of chickens

Feed efficiency is one of the most economically significant traits in a breeding program. Apparent metabolizable energy is the most used method to evaluate energy utilization for feed efficiency. The purpose of this study was to identify candidate genes of chickens with divergent apparent metabolizable energy by bioinformatics analysis. The gene expression profile of duodenal of the highest and lowest apparent metabolizable energy-ranked birds were analyzed. Differentially expressed genes were picked out using GEO2R tool. Gene ontology and pathway analysis were performed using bioinformatics tools. Cytoscape software was used to visualize protein-protein network. There were 201 DEGs, including 99 up-regulated genes enriched in metabolic pathways, Cellular senescence and Focal adhesion, and 102 down-regulated genes enriched in metabolic pathways, Regulation of actin cytoskeleton, Neuroactive ligand-receptor interaction, Calcium signaling pathway and Focal adhesion. Two important modules were detected and pathway enrichment analysis showed that they were mainly associated with Focal adhesion, Regulation of actin cytoskeleton and RNA transport. Fifteen hub genes were selected and among them, ITGA8, CDC42 and GSK3B might be the core genes related to apparent metabolizable energy of chickens. These hub genes can be used as biomarkers for apparent metabolizable energy and feed efficiency in breeding program of chickens.

Regulating appetite in broilers for improving body and muscle development - A review

Appetite is the desire for feed and water and the voluntary intake of feed and is an important regulator of livestock productivity and animal health. Economic traits such as growth rate and muscle development (meat deposition) in broilers are directly correlated to appetite. Factors that may influence appetite include environmental factors, such as stress and temperature variation, and animal‐specific factors, such as learning period, eating capacity and preferences. Feed preferences have been reported to be determined in early life, and this period is important in broilers due to their fast growth and relatively short growth trajectories. This may be of importance when contemplating the use of more circular and sustainable feeds and the optimization of appetite for these feeds. The objective of this review was to review the biological mechanisms underlying appetite using data from human, animal and bird models and to consider the option for modulating appetite particularly as it relates to broiler chickens.

Physiological and Pathological Mitochondrial Clearance Is Related to Pectoralis Major Muscle Pathogenesis in Broilers With Wooden Breast Syndrome

Wooden breast syndrome (WB) constitutes an emerging myopathy in the pectoralis major muscle (PM) of broiler chickens, characterized by myofiber hypertrophy and degeneration along with severe fibrosis. WB pathogenesis has been considered to involve hypoxia induced by rapid growth of the PM. In this study, we focused on mitochondrial morphology and dynamics in the myofibers, as these organelles are sensitive to damage by hypoxia, and examined the effects on WB pathogenesis. Specifically, the PMs of a flock of 35 broilers at 50 days of age were evaluated. First, the severity of disease in each bird was determined by measuring histopathological indices including the fibrotic area (FA) in the muscle and circularity of myofibers (CM). These values were 29.4 ± 9.6% and 0.70 ± 0.042, respectively, showing variety among the flock. Myofiber vacuolization was observed in all birds including numerous small- or large-rimmed vacuoles, with the former consisting of ultrastructurally autophagosome-like vacuoles engulfing degenerated mitochondria. The large-rimmed vacuoles frequently occurred in the PMs with more severe FA and CM, indicating a relationship between altered autophagy/mitophagy and WB severity. Next, the expression levels of hypoxia-adaptive and mitochondrial dynamics-related genes were analyzed, and their correlations with the histopathological indices were examined. The histopathological indices were negatively correlated with the expression of vascular endothelial growth factor A (VEGFA), indicating that less angiogenesis owing to weakened hypoxia-inducible factor signaling induces more severe WB pathology. In addition, the observed negative correlation with mitochondrial dynamics-related genes implied that WB pathology deteriorates concomitant with reduced mitochondrial dynamics. Furthermore, the expression of mitochondrial dynamics-related genes showed strong positive correlation with that of VEGFA and autophagy-/mitophagy-related genes. These results revealed that the PMs of broilers possess the mechanism of physiological clearance of mitochondria damaged by the hypoxia resulting from the continuous mitochondrial dynamics and autophagy/mitophagy accompanying rapid PM growth. In turn, the altered mitochondrial clearance induced by chronic hypoxia and the accumulation of damaged mitochondria likely underly the severe pathological features of WB.

Phytogenic feed- and water-additives improve feed efficiency in broilers via modulation of (an)orexigenic hypothalamic neuropeptide expression

Fueled by consumer preference for natural and antibiotic-free products, phytogenics have become the fastest growing segment of the animal feed additives. Yet, their modes of action are not fully understood. This study was undertaken to determine the effect of 5 phytogenics (3 feed- and 2 water-supplements) on the growth performance of commercial broilers, and their potential underlying molecular mechanisms. Day-old male Cobb 500 chicks (n = 576) were randomly assigned into 48 pens consisting of 6 treatments (Control; AVHGP; SCP; BHGP; AVSSL; SG) in a complete randomized design (12 birds/pen, 8 pens/treatment, 96 birds/treatment). Chicks had ad libitum access to feed and water. Individual body weight (BW) was recorded weekly and feed intake was measured daily. Core body temperatures were continuously recorded using thermo-loggers. At d 35, hypothalamic tissues were excised from the thermo-logger-equipped chickens (n = 8 birds/treatment) to determine the expression of feeding-related neuropeptides. Both feed (AVHGP, SCP, BHGP) and water-supplemented (AVSSL, SG) phytogenics significantly improved feed efficiency (FE) compared to the control birds. This higher FE was achieved via a reduction in core body temperature and improvement of market BW, without changes in feed intake in broilers supplemented with phytogenic water additives as compared to the control group. Broilers fed dietary phytogenics, however, attained higher feed efficiency via a reduction in feed intake while maintaining similar BW as the control group. At the molecular levels, the effects of the phytogenic water additives seemed to be mediated by the activation of the hypothalamic AgRP-ORX-mTOR-S6k1 and inhibition of CRH pathways. The effect of the phytogenic feed additives appeared to be exerted through the activation of AdipoQ, STAT3, AMPK, and MC1R pathways. This is the first report describing the likely central mechanisms through which phytogenic additives improve the growth performance and feed efficiency in broilers.

Dynamics of gene expression of hormones involved in the growth of broiler chickens in response to the dietary protein and energy changes

The synergy between the genetic potential and the nutrient intake determines the growth performance of meat-type chicken and nutrigenomics approach helps us understand the response of candidate genes of growth in chicken to dietary manipulations. The current study aimed to assess the growth performance and expression of hepatic growth related genes in the naked neck broiler chicken in response to different dietary energy and protein levels with a hypothesis that high plane of nutrition enhances both of these positively. The results revealed that birds have shown significantly better growth performance under high protein (HP) and high energy (HE) dietary regime. The expression profiles of the genes studied revealed upregulation of IGF-1, IGF-2, and GH under dietary HP and HE regime relative to other protein and energy levels with greater upregulation at 3rd week than the 1st and 5th week of age of birds. The IGFR and GHR mRNA expression was significantly higher under HP and HE dietary regimen with an increasing and decreasing trend from 1st to 5th week of age, respectively. A consistent and significant downregulation of IGFBP-2 was observed under HP and HE regime throughout the feeding trial. The myostatin expression was higher at 3rd week of age followed by 1st week expression. The HP and HE as well as LP (Low protein) and HE diet resulted in significant upregulation of myostatin gene expression in liver. In support to the set hypothesis of this study the high protein and high energy diet resulted in better growth performance of broiler chickens with corresponding upregulation of IGF-1, IGF-2, IGFR, GH, GHR, and Myostatin gene expression and downregulation of IGFBP-2 in liver.

Evaluation of novel protease enzymes on growth performance and nutrient digestibility of poultry: enzyme dose response

Two experiments were conducted to evaluate 3 novel proteases in broilers. In experiment 1, 600 male, Cobb 500 broilers were allocated to 1 of 12 experimental diets (5 birds/pen and 10 replicates/diet). A control (C) diet was formulated to be adequate in all nutrients. Proteases 1, 2, or 3 were added to this diet at 3 doses (1x, 3x, or 9x) in a 3 × 3 factorial arrangement of treatments. The factorial was augmented with 2 treatments of phytase at 500 or 1,500 FTU/kg added to the C diet. In experiment 2, 2,050 male Ross 308 broilers were allocated to 1 of 10 experimental diets (25 birds/pen and 9 replicates/diet). A C diet was formulated to be adequate in all nutrients. Protease 1, 2, or 3 was then added to the C diet at 3 doses (1x, 2x, or 4x) in a 3 × 3 factorial arrangement of treatments plus the C. In experiment 1, birds fed phytase gained more (P < 0.05) than birds fed protease, but neither were different than birds fed the C. Supplementation of 9x dose of any protease resulted in a reduction (P < 0.05) in BWG when compared with birds fed 1x dose of protease or phytase at 500 or 1,500 FTU/kg. Feed conversion ratio was improved (P < 0.05) in birds fed phytase compared with birds fed the C diet. Nitrogen digestibility was greater (P < 0.05) in birds fed protease 1 when compared with birds fed protease 2. Birds fed the 1x dose of protease or 500 FTU/kg of phytase had a greater (P < 0.05) N digestibility than birds fed 3x dose of protease. In experiment 2, protease supplementation significantly reduced (P < 0.05) BWG when compared with birds fed the C from hatch to 35 D post-hatch. Protease supplementation did not improve broiler growth performance or N digestibility above that of a nutrient adequate control diet or a diet supplemented with 500 FTU/kg of phytase.

Research Note: The effect of selection for 16-week body weight on turkey serum metabolome

The phenotype of modern commercial turkeys is substantially different than that of unselected, heritage turkey lines. These phenotypic changes have arisen from alterations in the genome/transcriptome, as well as the influence of many external factors on growth performance including nutrition, environment, and management. To investigate the phenotypic changes resulting from genetic selection for increased body weight, The Ohio State University maintains 2 unique genetic turkey lines: the randombred control (RBC2) line, which is comprised of genetics from 1960 era commercial turkeys and has been maintained without conscious selection for any trait; and the F line, which was originally selected from the RBC2 line and has been selected for increased 16 wk body weight for over 50 generations. This study used broad-spectrum mass-spectrometry profiling techniques to identify and quantify differences in the metabolome of the serum of F and RBC2 turkey lines. Serum samples from both F and RBC2 turkeys were subject to quantitative time of flight liquid chromatography tandem mass spectrometry analyses. Principle component analyses showed distinct populations of metabolites in the F vs. RBC2 serum, suggesting that increased body weight is associated with the accumulation of several metabolites. Comparing the spectral features to online databases resulted in the selection of 104 features with potentially identifiable chemical structures. Of these 104 features, 25 were found at higher levels in the serum of the RBC2 line turkeys, while 79 were found at a greater abundance in the F line turkeys. A more detailed analysis of these 104 features allowed for the putative identification of 49 compounds, which were clustered into 6 functional groups: 1) energy metabolism; 2) vitamins; 3) hormones and signaling molecules; 4) lipid derivatives, fatty acid metabolites, and membrane components; 5) amino acid/protein metabolism; and 6) microbial metabolites. Further validation and experimentation is needed to confirm the identity of these metabolites and understand their biological relevance and association with selection for increased body weight.

Is a Single Nucleotide Polymorphism Marker in the Cholecystokinin A Receptor Gene Practically Suitable for Improving the Growth Traits of Hinai-jidori Chickens?

We have previously reported a significant association between the single-nucleotide polymorphism (SNP; g.420 C>A) in the cholecystokinin type A receptor gene (CCKAR) and the growth traits of Hinai-dori, a breed of chicken that is indigenous to Japan. Moreover, we have demonstrated that the minor allele of this SNP improved the growth rate in a low-growth line of the Hinai-dori breed. Hence, in the present study, we verified the association between this SNP and the growth traits of the Hinai-jidori chicken: a cross between a Hinai-dori sire and Rhode Island Red dam. In addition, we verified whether the growth rate was improved in Hinai-jidori chickens produced from the parent stocks in which the SNP A/A genotype was fixed by selection (improved Hinai-jidori chickens). The Hinai-jidori female chicks at 4 weeks of age, were subdivided into three genotypic groups (A/A, A/C, and C/C), with 20 chicks in each group, and reared in an open-sided poultry shed until 23 weeks of age. The results showed that the body weight at 23 weeks of age and the average daily gain after 14 weeks of age were significantly higher in group A/A than in group C/C. Subsequently, the improved and the conventional Hinai-jidori chickens were reared until they reached 22 weeks of age to verify the effects on their growth traits. The body weight of the improved Hinai-jidori chickens at 22 weeks was significantly greater than the conventional Hinai-jidori chickens. Moreover, the association between the SNP and body weights of Hinai-jidori chickens at market age (24 weeks) on the production farms showed that the A allele was significantly superior to the C allele. In conclusion, the CCKAR g.420 C>A SNP improves the growth rate of commercial Hinai-jidori chickens and could be a candidate marker for improving the growth performance in selective breeding of Hinai-jidori chickens.

Effects of dietary energy and protein content and lipid source on growth performance and carcass traits in Pekin ducks

The present study was conducted to determine the impact of dietary energy and protein concentrations and lipid sources on growth performance and carcass traits of Pekin ducks. In Exp. 1, 15-day-old ducks (6 replicate pens, 60 ducks/pen) were randomly assigned to 4 dietary treatments with different metabolizable energy (ME) and crude protein (CP) concentrations (2,850 kcal/kg and 16%, 2,950 kcal/kg and 16.5%, 3,050 kcal/kg and 17.0%, and 3,150 kcal/kg and 17.5%) based on body weight (BW). In Exp. 2, 20-day-old ducks (4 replicate pens, 60 ducks/pen) were randomly allotted to 3 dietary fat sources (soybean oil, lard, and palm oil) with or without emulsifier in a 3 × 2 factorial arrangement. In Exp. 1, increasing ME and CP level improved (P < 0.05) body weight gain (BWG) and cost-to-gain ratio linearly, but reduced (P < 0.05) feed intake (FI) and feed-to-gain ratio (F/G) linearly. Breast skin thickness and liver redness (a*) value increased (P < 0.05) linearly with the increasing ME and CP level. In Exp. 2, no interactions between fat sources and emulsifier were observed. Feeding lard and palm oil diets increased (P < 0.05) final BW and BWG compared to soybean oil. Birds fed soybean oil and palm oil diets had lower (P < 0.05) FI compared to those fed lard diet. F/G in soybean oil and lard groups was higher (P < 0.05) compared to palm oil group. Birds in palm oil and lard groups had higher (P < 0.05) European production efficiency factor than those in soybean oil group. The addition of emulsifier increased (P < 0.05) BWG. In summary, the optimal ME and CP level for roasting was 2,950 kcal/kg ME and 16.5% CP and the palm oil was better than soybean oil and lard in Pekin ducks from 15 to 40 D of age.

Effects of lysophospholipid on growth performance, carcass yield, intestinal development, and bone quality in broilers

A study was conducted to evaluate the effects of supplementing different levels of lysophospholipid (LPL) to normal or reduced energy diets on growth performance, carcass yield, intestinal morphology, and skeletal development in broilers. A total of 960 one-day-old Cobb 500 male birds were allocated using a 2 × 4 factorial arrangement with 2 energy levels (NE: normal and RE: 100 kcal/kg metabolizable energy reduction) and 4 LPL supplement levels (0, 0.025, 0.050, and 0.075%). Three diet phases were fed throughout the trial: starter (days 0 to 7), grower (days 8 to 21), and finisher (days 22 to 42) phases. Body weight (BW), feed intake (FI), and feed conversion ratio were calculated at the end of each phase. At day 7 and 21, duodenum and jejunum samples were collected for intestinal morphology and claudin-3 expression analyses, and tibia were sampled for bone quality analyses. At day 42, 4 birds per replicate were selected to measure carcass yield. The results showed low metabolizable energy diets impaired bird's growth performance, intestine development, and bone quality. The 0.075% LPL supplement in NE improved BW, BW gain, and FI in the finisher and overall period compared with no LPL supplement in NE (P < 0.05). In RE, the 0.025% LPL supplement significantly improved growth performance compared to the other treatments in RE (P < 0.05). The interactions on processing parameters were detected with LPL supplement in NE diets; 0.025, 0.05, and 0.075% LPL supplements significantly increased pectoral major percentages compared to the one without LPL supplement in NE (P < 0.05). The 0.075% LPL supplement increased dressing percentage (cold carcass weight/live BW) compared with the others (P < 0.05). The intestine morphology results showed LPL had positive effects on intestine development mainly during the early age (day 7) and claudin-3 expression at both day 7 and 21. Furthermore, LPL supplement significantly increased the total Ca and P deposition and positively affected the bone structure development. In summary, dietary LPL supplementation promoted growth performance, carcass yield, intestinal development, intestinal health, and bone quality.